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  • Writer's pictureDr. Lauren

What is Intermittent Fasting?

Updated: Feb 7, 2023

Have you heard about Intermittent Fasting and been wondering if it’s worth all they hype? Maybe someone suggested you try it but, you’ve been on the fence about whether you should try it?


today I’m going to give you the skinny on Intermittent Fasting.

Have you ever thought?

But isn’t breakfast the most important meal of the day?

I thought I was suppose to eat 6 small meals a day?

Won’t I be starving?

I hear these questions consistently when patients are asking about the idea of intermittent fasting. So today, I’ll give you the run down on intermittent fasting.

What is Intermittent Fasting?

Intermittent fasting is a style or pattern of eating with ‘windows’ of eating and not eating. There are different styles of fasting schedules with intermittent calorie restriction. The 3 most common types are:

Alternate Day Fasting (ADF)

Alternating “Fast” and “Feast” days. This eating model is based on feast days where food consumption is based on hunger or fast days, where caloric consumption is less than 25% of normal. This type of eating pattern is not appropriate for Type-1 Diabetics, women who are pregnant or breastfeeding, or those individuals requiring regular food intake to take medications.

Periodic Fasting (PF) or Intermittent Calorie Restriction (ICF)

PF or ICF is fasting for up to 24hrs once or twice per week with no measured caloric intake on other (non-fasting) days.

Time Restricted Fasting (TRF)

Perhaps the most common trend, TRF establishes a feeding window throughout each day (usually 6-10hrs) with a 14-18hr daily fast. So how would this look? Maybe you get home late and don’t finish eating dinner till 8pm. That’s ok, you’re eating window starts at noon the next day. Or you have small children that eat early and you’re done by 6 pm. Your fasting window would be 6pm-10am and your eating window between 10am and 6pm.

If you’ve never tried IF, maybe think about starting with a14hr fast (with a 10hr feeding window). Ie. 8pm to 10am . This can help you dip your toes in the water of IF. Then you can always work up to the gold standard 16 hour fast from there.

Benefits of IF

Research has show the most benefit in regards to IF with Weight loss and fat loss and improved lipid profiles by reducing our LDL and Triglyceridies. Some proposed benefits are improved energy, focus, performance, productivity, anti- aging, and even provide an anti-inflammatory benefits. These improvements may also benefit gut microbiotial diversity possible blood sugar balancing and have beneficial effects on insulin sensitivity,

How Long Should I fast before I see results?

Bottom line, when considering IF you must think about what type of IF plan would work best for you in terms of your ability to sustain this type of eating pattern for at least 12 weeks. 12 weeks is the time frame for most studies that have shown benefits in terms of weight loss using IF. Other considerations are your lifestyle, work and how it may impact your family. The most important thing is to try and keep a schedule that is consistent. A plan that isn’t going to be executed regularly isn’t going to be successful at all.

Should women fast? Does the IF window differ if you’re a woman?

There is a suggestion that IF may affect women’s hormones and cause changes in their menstrual cycles. There is some data to support this, however it may be due to IF not being carried out correctly or healthfully. IF done incorrectly may exacerbate hormone issues if a woman is already low in some of her micronutrients or experiencing protein and fat deficiencies. Just like any healthy dietary plan, it’s still essential to balance our micro and macronutrient status during IF. The only difference is that we’re eating a balanced diet in an eating window.

What Can or Can’t I have while fasting?

During a fasted state, technically you can not eat or consume anything with any measurable caloric value. Your metabolism is very smart and any rise in insulin will break a fast. So any carbohydrate or minimal amount of protein or fat, will in theory break a fast. So items that will NOT break your fast are:

  • Water, carbonated water

  • Black Coffee has zero calories.

  • Green Tea

  • Stevia

  • Creatine

  • Glutamine

There is another school of thought, that if your goal is weight loss, anything less than 50kcal will minimally stimulate your metabolism and you will still maintain the physiological benefits of fasting. So if you have to put some almond milk or cream in your coffee, make sure it’s less than 50kcal.

Items that WILL break your fast and likely cause a spike in insulin:

  • Cream

  • Medium-chain Triglycerides

  • Coconut Oil

  • Bulletproof coffee (butter/ghee/MCTs)

  • Herbal Teas that contain fruit juice

  • Bone broth

  • Collagen

  • Protein powders

  • BCAAs and Pre-Workout Drinks

  • Exogenous Ketones

  • CBD Oils

  • Greens Powders

  • Truvia/erythritol, maltodexrin, dextrose

When is comes to Apple Cider Vinegar (ACV) and or Lemon Juice we’re still unsure if they cause issues with fasting. Technically ACV does have calories, but it also helps to limit glucose absorption while lemon juice may yield only a limited insulin response. So the likelihood is that both would have minimal effect on the fasted state.

The bottom line is that anything with calories technically breaks a fast, however it’s a question of whether less than 50cal in a fasted state will matter physiologically. The best thing to do is try it and see how it goes. If you don’t feel like your getting the positive benefits from IF, you may need to remove the cream from you morning coffee.

How Do I Break a Fast?

The rule of thumb when coming out of a fasted state is to provide your body with a balanced meal of protein, fat and carbohydrates. This will stimulate your metabolism and fuel your body with essential nutrition. I usually recommend having a nice serving of protein (15-20g). So a protein smoothie would work really nicely to break a fast or balanced meal of leftovers.

Who is IF Not For?

Just remember, IF is not for Pregnant and or Breastfeeding women, Type 1 diabetics or individuals who have to take medication with food.

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